Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$220.34	9.775%	$241.8782	$241.88	$241.90	$241.90
Purchase #2	$15.56	10.548%	$17.2013	$17.20	$17.20	$17.20
Purchase #3	$227.72	11.533%	$253.9829	$253.98	$254.00	$254.00
Purchase #4	$184.71	3.178%	$190.5801	$190.58	$190.60	$190.60
Purchase #5	$80.81	6.443%	$86.0166	$86.02	$86.00	$86.00
Purchase #6	$29.54	6.132%	$31.3514	$31.35	$31.35	$31.40
Purchase #7	$221.54	8.674%	$240.7564	$240.76	$240.75	$240.80
7 purchase totals =	$980.22		$1,061.7669	$1,061.77	$1,061.80	$1,061.90